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  • 1
    Publication Date: 2021-05-12
    Description: In order to monitor temporal and spatial crustal activities associated with earthquakes, ground- and satellite-based monitoring systems have been installed in China since the 1990s. In recent years, the correlation between monitoring strain anomalies and local major earthquakes has been verified. In this study, we further evaluate the possibility of strain anomalies containing earthquake precursors by using Receiver Operating Characteristic (ROC) prediction. First, strain network anomalies were extracted in the borehole strain data recorded in Western China during 2010–2017. Then, we proposed a new prediction strategy characterized by the number of network anomalies in an anomaly window, Nano, and the length of alarm window, Talm. We assumed that clusters of network anomalies indicate a probability increase of an impending earthquake, and consequently, the alarm window would be the duration during which a possible earthquake would occur. The Area Under the ROC Curve (AUC) between true predicted rate, tpr, and false alarm rate, fpr, is measured to evaluate the efficiency of the prediction strategies. We found that the optimal strategy of short-term forecasts was established by setting the number of anomalies greater than 7 within 14 days and the alarm window at one day. The results further show the prediction strategy performs significantly better when there are frequent enhanced network anomalies prior to the larger earthquakes surrounding the strain network region. The ROC detection indicates that strain data possibly contain the precursory information associated with major earthquakes and highlights the potential for short-term earthquake forecasting.
    Description: National Natural Science Foundation of China under Grant 41974084 Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, under its observation and Research Program for Prediction of Earthquakes and Volcanic Eruptions.
    Description: Published
    Description: 515
    Description: 7T. Variazioni delle caratteristiche crostali e precursori sismici
    Description: JCR Journal
    Keywords: receiver operating characteristic ; a new prediction strategy ; frequent network anomalies ; prediction efficiency ; short-term earthquake forecasting ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2021-10-28
    Description: In this paper, based on non-negative matrix factorization (NMF), we analyzed the ionosphere magnetic field data of the Swarm Alpha satellite before the 2016 (Mw = 7. 8) Ecuador earthquake (April 16, 0.35°N, 79.93°W), including the whole data collected under quiet and disturbed geomagnetic conditions. The data from each track were decomposed into basis features and their corresponding weights. We found that the energy and entropy of one of the weight components were more concentrated inside the earthquake-sensitive area, which meant that this weight component was more likely to reflect the activity inside the earthquake-sensitive area. We focused on this weight component and used five times the root mean square (RMS) to extract the anomalies. We found that for this weight component, the cumulative number of tracks, which had anomalies inside the earthquake-sensitive area, showed accelerated growth before the Ecuador earthquake and recovered to linear growth after the earthquake. To verify that the accelerated cumulative anomaly was possibly associated with the earthquake, we excluded the influence of the geomagnetic activity and plasma bubble. Through the random earthquake study and low-seismicity period study, we found that the accelerated cumulative anomaly was not obtained by chance. Moreover, we observed that the cumulative Benioff strain S, which reflected the lithosphere activity, had acceleration behavior similar to the accelerated cumulative anomaly of the ionosphere magnetic field, which suggested that the anomaly that we obtained was possibly associated with the Ecuador earthquake and could be described by one of the Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) models.
    Description: This research was supported by the National Natural Science Foundation of China under Grant No. 41974084 and the International Cooperation Project of Department of Science and Technology of Jilin Province No. 20200801036GH.
    Description: Published
    Description: 621976
    Description: 7T. Variazioni delle caratteristiche crostali e "precursori"
    Description: JCR Journal
    Keywords: Ecuador earthquake ; cumulative number of anomalous tracks ; Swarm satellites magnetic field ; non-negative matrix factorization decomposition ; 04.05. Geomagnetism ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2023-02-01
    Description: Nowadays, the possibility that medium-large earthquakes could produce some electromagnetic ionospheric disturbances during their preparatory phase is controversial in the scientific community. Some previous works using satellite data from DEMETER, Swarm and, recently, CSES provided several pieces of evidence supporting the existence of such precursory phenomena in terms of single case studies and statical analyses. In this work, we applied a Worldwide Statistical Correlation approach to M5.5+ shallow earthquakes using the first 8 years of Swarm (i.e., from November 2013 to November 2021) magnetic field and electron density signals in order to improve the significance of previous statistical studies and provide some new results on how earthquake features could influence ionospheric electromagnetic disturbances. We implemented new methodologies based on the hypothesis that the anticipation time of anomalies of larger earthquakes is usually longer than that of anomalies of smaller magnitude. We also considered the signal’s frequency to introduce a new identification criterion for the anomalies. We find that taking into account the frequency can improve the statistical significance (up to 25% for magnetic data and up to 100% for electron density). Furthermore, we noted that the frequency of the Swarm magnetic field signal of possible precursor anomalies seems to slightly increase as the earthquake is approaching. Finally, we checked a possible relationship between the frequency of the detected anomalies and earthquake features. The earthquake focal mechanism seems to have a low or null influence on the frequency of the detected anomalies, while the epicenter location appears to play an important role. In fact, land earthquakes are more likely to be preceded by slower (lower frequency) magnetic field signals, whereas sea seismic events show a higher probability of being preceded by faster (higher frequency) magnetic field signals.
    Description: Published
    Description: 2649
    Description: 7T. Variazioni delle caratteristiche crostali e "precursori"
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: 5IT. Osservazioni satellitari
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2023-02-02
    Description: A nonnegative tensor decomposition (NTD) approach has been developed to analyze the ionospheric magnetic field data of the Swarm Alpha and Charlie satellites for the Mw7.8 2015 Nepal earthquake. All available satellite data were analyzed regardless of geomagnetic activity. We used the amplitude time–frequency spectra of the two-satellite data to build third-order tensors and decomposed them into three components. One of these components seems to be more affected by seismicity. In particular, the cumulative number of anomalous tracks of this component displays accelerated growth that conforms to a sigmoid fit from 60 to 40 days before the mainshock. Subsequently, until ten days before the earthquake, it shows a weak accelerating trend that obeys a power-law behavior and then resumes linear growth after the mainshock. Moreover, the cumulative anomaly was indicated not to be caused by geomagnetic activity, solar activity, or other nonseismic factors. An investigation of the foreshocks around the epicenter reveals that the cumulative Benioff strain also exhibited two accelerated growths before the mainshock, which is consistent with the cumulative result of ionospheric anomalies. In the first acceleration stage, seismicity appeared in the region surrounding the epicenter, and most of the ionospheric anomalies were offset away from the epicenter. During the second acceleration stage, some foreshocks occurred closer to or on the mainshock fault, and ionospheric anomalies also appeared near two faults around the epicenter. Furthermore, the correspondence between the ionospheric anomalies and the anomalies in different geolayers can be explained by the lithosphere–atmosphere–ionosphere coupling model.
    Description: Published
    Description: 2006119
    Description: 7T. Variazioni delle caratteristiche crostali e "precursori"
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: 2015 Nepal earthquake ; Swarm satellite magnetic field data ; non-negative tensor decomposition ; precursors ; instability activities on fault ; 04.06. Seismology ; 01.02. Ionosphere ; 04.05. Geomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
    Publication Date: 2024-01-08
    Description: In this paper, we provide a characterisation of the ionosphere from April 2018 to September 2022 for 48 investigated months. We used the data of the China Seismo Electromagnetic Satellite (CSES-01), which is a sun-synchronous satellite with five days of revisit time and fixed local time of about 2 a.m. and 2 p.m. The unique orbit of CSES-01 permitted us to produce a monthly background of the ionosphere for night- and daytime with median values acquired during geomagnetic quiet time in equatorial and mid-latitude regions (i.e., between 50° S and 50° N of geographical latitude). We compared the obtained CSES-01 monthly median values with the solar activity in terms of sunspot numbers, and we found a high correlation of 0.89 for nighttime and 0.85 for daytime between the mean sunspot number and the maximum of the characterised CSES-01 Ne map values. In addition, we extracted all the anomalous positive increases in CSES-01 electron density and compared them with the Worldwide M5.5+ shallow earthquakes. We tested two different definitions of anomaly based on median and interquartile range or (mild) outliers. We tried two relationships between anomalies inside Dobrovolsky’s area before the earthquake and the magnitude of the same seismic events: one which considers distance in space and time and a second which only uses the anticipation time of the anomaly before the earthquake. Using both anomaly definitions, we searched the best coefficients for these two laws for mid-latitude and equational regions. We found that the best coefficients are independent of the anomaly definition, but better accuracy (greater than 80%) is obtained for the outlier definition. Finally, using receiving operating characteristic (ROC) curves, we show that CSES-01 increases seem statistically correlated to the incoming seismic activity.
    Description: Published
    Description: 1527
    Description: OST4 Descrizione in tempo reale del terremoto, del maremoto, loro predicibilità e impatto
    Description: OSA3: Climatologia e meteorologia spaziale
    Description: JCR Journal
    Keywords: CSES ; electron density ; earthquake ; ionosphere ; satellite background ; 01.02. Ionosphere ; 04.06. Seismology ; 05.07. Space and Planetary sciences
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2008-12-01
    Print ISSN: 1672-7975
    Electronic ISSN: 1993-0658
    Topics: Geosciences , Physics
    Published by Springer
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  • 7
    Publication Date: 2020-09-27
    Description: To investigate the nonlinear spatio-temporal behavior of earthquakes, a complex network has been built using borehole strain data from the southwestern endpoint of the Longmenshan fault zone, Sichuan-Yunnan region of China, and the topological structural properties of the network have been investigated based on data from 2011–2014. Herein, six observation sites were defined as nodes and their edges as the connections between them. We introduced Multi-channel Singular Spectrum Analysis (MSSA) to analyze periodic oscillations, earthquake-related strain, and noise in multi-site observations, and then defined the edges of the network by calculating the correlations between sites. The results of the daily degree centrality of the borehole strain network indicated that the strain network anomalies were correlatable with local seismicity associate with the earthquake energy in the strain network. Further investigation showed that strain network anomalies were more likely to appear before major earthquakes rather than after them, particularly within 30 days before an event. Anomaly acceleration rates were also found to be related to earthquake energy. This study has revealed the self-organizing pre-earthquake phenomena and verified the construction of borehole networks is a powerful tool for providing information on earthquake precursors and the dynamics of complex fault systems.
    Electronic ISSN: 1099-4300
    Topics: Chemistry and Pharmacology , Physics
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  • 8
    Publication Date: 2020-01-11
    Description: Infrared and visible image fusion can obtain combined images with salient hidden objectives and abundant visible details simultaneously. In this paper, we propose a novel method for infrared and visible image fusion with a deep learning framework based on a generative adversarial network (GAN) and a residual network (ResNet). The fusion is accomplished with an adversarial game and directed by the unique loss functions. The generator with residual blocks and skip connections can extract deep features of source image pairs and generate an elementary fused image with infrared thermal radiation information and visible texture information, and more details in visible images are added to the final images through the discriminator. It is unnecessary to design the activity level measurements and fusion rules manually, which are now implemented automatically. Also, there are no complicated multi-scale transforms in this method, so the computational cost and complexity can be reduced. Experiment results demonstrate that the proposed method eventually gets desirable images, achieving better performance in objective assessment and visual quality compared with nine representative infrared and visible image fusion methods.
    Electronic ISSN: 2076-3417
    Topics: Natural Sciences in General
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  • 9
    Publication Date: 2016-04-12
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
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  • 10
    Publication Date: 2018-09-05
    Print ISSN: 1593-5213
    Electronic ISSN: 2037-416X
    Topics: Geosciences
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